This invention relates to a wire bonding apparatus for connecting between electrodes and external leads of semiconductor integrated circuit elements, such as ICs or LSI circuits, by bonding wires placed in position by appropriate ultrasonic waves from an ultrasonic horn.
In the assembly of semiconductor integrated circuit elements, a wire bonding step is included for connecting between the electrodes of a semiconductor pellet and the external leads of the circuit elements. Conventionally, a wire bonding apparatus has been used. Ultrasonic wave oscillation from an ultrasonic horn is provided to place a bonding wire between the electrodes of the semiconductor pellet located in the center of a lead frame supported on a heat block and the external leads.
However, the wire bonding step is very delicate and requires a wire bonding apparatus capable of performing very precise operations, for instance, contact bonding a 100 um diameter wire ball to a 100 um square aluminum pad. It is therefore necessary to minimize locational errors with regard to respective positions of the semiconductor pellet, the external leads, and the wire bonding apparatus.
For keeping the locational errors within a predetermined tolerance, certain design changes in the wire bonding apparatus of the prior art have been considered, such as making the operating pitch of an X-Y table closer or pattern recognition resolution finer. However, there are limitations in the above design changes, and, therefore, with the miniaturization of the electrode (the semiconductor pellet) in recent years, conventional wire bonding apparatus have had problems in that it is impossible to keep the locational error of the bonding location within a tolerance of about 5 .mu.m.